Retina I loose front lens element

[Ken_L]

I have a Retina I (type 10) with the Schneider Xenar 3.5 lens, and the front element of the lens is loose.

The front element will move from side-to-side about 1/4 inch, and also moves from front to back about 1/8 inch. I unscrewed the front lens assembly from the camera, and found the rear half of the front assembly is tight and screwed all the way in. Note that this rear half is the piece that contains the center element of the lens.

I unscrewed the rear part of the assembly to access the inside of the lens assembly, and found that there is a ledge on the inside of the front retaining ring to position the front element. When I placed the front element on this ledge, the lens would not move; however when I replaced the rear part of the assembly, the front element is loose. Obviously, there is a gap large enough between the front retaining ring and the rear part of the lens assembly that allows the front element to move.

My first question is how to secure the front element. Was there originally a gasket/shim of some sort to hold the front element in place? (If there was, it is missing.) Or should I tighten the front retaining ring just enough to secure the front element?

My second question concerns adjusting the focus. Is the focal point of the assembly based on the position of the front retaining ring, or is it based on the front element being against the rear portion of the assembly? I tend to think it's the latter, as the rear part was originally screwed in fully and it has a definite 'stop point' at which it is tight and can't be screwed in any further. (There is a knurled rim at the back of the rear piece, which acts as a screw head to stop any further movement.)

I haven't moved the front retaining ring at all so far, so I have left myself a reference point of sorts.

Thanks.

Ken